Students from nearby Rosary High School, an all-girls sister school, were dancing when the stage buckled. Injuries included broken bones, bruises, and scrapes.

The likely cause ‘‘at this point looks like too many students and too much weight on the platform stage,’’ Anaheim police Lieutenant Tim Schmidt told City News Service on Sunday.

Investigators will double-check the school’s stage permit to determine if it included a weight restriction or a limit on the number of people who could be on stage, Schmidt said.

About 500 students and parents were in the auditorium at the time of the collapse.

The students were performing in ‘‘Red and Gold,’’ Rosary High’s annual musical theater challenge since 1971, in which teams prepare for six weeks to put on choral, dance, drama, and other performances, according to the school’s website.